1. Field of the Invention
This invention relates to a connecting mechanism for a thin stainless steel pipe and a joint which can simply and securely connect the thin stainless steel pipe and the joint in the field and can easily know a flaw of a coupling work.
2. Description of the Related Art
This kind of related art includes a structure disclosed in Japanese Utility Model Publication No. 2-37015 (patent document 1) which has been proposed by the applicant of the present application in advance. When describing based on FIG. 10 showing a connecting structure for a thin stainless steel pipe and a joint which is obtained by further adding an improvement to this related art, this related art is constructed by a thin stainless steel pipe 1 in which a chevron type projection portion 5 having two inclined surfaces 5a and 5b is formed in an outer periphery of an end portion, a joint 2 in which a male thread portion 7 is formed in an outer peripheral surface of an end portion as well as having an inner diameter to which the thin stainless steel pipe 1 is inserted, a nut 4 which has a female thread portion 8 engaging with the male thread portion 7 of the joint 2 as well as having a fitting portion 11 outwardly fitted to the thin stainless steel pipe 1 so as to oppose to the joint 2 on the boundary of the chevron type projection portion 5, and a packing 3 which is provided between the joint 2 and the thin stainless steel pipe 1.
In the joint 2, there is formed a packing fitting portion 6 for fitting the packing 3 closely attached to one inclined surface 5b close to the end portion of the chevron type projection portion 5 to an inner periphery close to an open end portion 2a thereof. Further, a pipe insertion hole 2d expanded at a thickness of the thin stainless steel pipe 1 for inserting an end portion of the thin stainless steel pipe 1 is formed in both ends of an inner hole 2c in a center portion.
In the nut 4, there is formed an inclined notch portion 10 closely attached to the other inclined surface 5a of the chevron type projection portion 5 in an inner end portion of the fitting portion 11 outwardly fitted to the thin stainless steel pipe 1, and there is formed a joint contact surface 9 with which the opening end portion 2a of the joint 2 is brought into contact at a time of screwing and firmly attaching the female thread portion 8 of the nut 4 and the male thread portion 7 of the joint 2. The joint contact surface 9 is formed based on an inner diameter difference between the fitting portion 11 and the female thread portion 8.
The packing 3 is formed in such a manner as to be closely attached to each of the one inclined surface 5b of the chevron type projection portion 5 formed in the thin stainless steel pipe 1 a time of screwing and firmly attaching the female thread portion 8 of the nut 4 and the male thread portion 7 of the joint 2, the joint contact surface 9 of the nut 4, and a packing pressing surface 6a and a packing outer peripheral contact surface 6b corresponding to an inner side surface of the packing fitting portion 6 of the joint 2, and is made of an elastic material such as a rubber or the like having an approximately polygonal horizontal cross sectional shape.
The chevron type projection portion 5 of the thin stainless steel pipe 1 is formed by using a pipe expanding apparatus K, as shown in FIG. 11, and is formed specifically in accordance with the following procedure. First of all, the female thread portion 8 of the nut 4 outwardly fitted to the thin stainless steel pipe 1 is screwed and firmly attached to a male thread portion 21 formed in an outer periphery of a pipe expanding head 20 fixed to an apparatus (not shown), a shaft 25 outwardly fitting a rubber receiver 22, a pipe expanding rubber 23 and a rubber presser foot 24 is movably inserted from an end portion of the thin stainless steel pipe 1, and a leading end of the thin stainless steel pipe 1 is inserted from an opening portion of the pipe expanding head 20 until it comes into contact with a step wall 20a in an inner portion thereof. Further, the rubber receiver 22 is brought into contact with the step wall 20a of the pipe expanding head 20 by pulling the shaft 25 by an apparatus (not shown) in an arrow direction, and the shaft 25 is pulled in the arrow direction, whereby the rubber presser foot 24 is pushed in the arrow direction by a locking portion 26 fixed to a leading end of the shaft 25. At this time, since the pipe expanding rubber 23 pinched by the rubber receiver 22 and the rubber presser foot 24 is reduced its width, the pipe expanding rubber 23 is expanded at a volume reduced in a circumferential direction. In an outer periphery of the expanded pipe expanding rubber 23, the thin stainless steel pipe 1 is evaginated to a chevron space U in an end portion thereof in accordance with the expansion in the circumferential direction of the pipe expanding rubber 23, as shown in FIG. 12, based on an existence of the chevron space U formed by the inclined notch portion 10 of the nut 4 and a notch portion 20b formed in an inner peripheral surface of a leading end of the pipe expanding head 20, whereby the chevron type projection portion 5 is formed. The nut 4 is loosened in this state so as to be detached from the pipe expanding head 20, and there is set a state in which the nut 4 is fitted to an outer periphery of the thin stainless steel 1. The shaft 25, and the rubber receiver 22, the pipe expanding rubber 23 and the rubber presser foot 24 which are outwardly fitted to the shaft 25 are drawn out from the thin stainless steel pipe 1.
The connection between the thin stainless steel pipe 1 and the joint 2 is achieved first of all by fitting the packing 3 from the end portion of the thin stainless steel pipe 1 so as to closely attach the fitted packing 3 to the one inclined surface 5a, or fitting the packing 3 into the packing fitting portion 6 of the joint 2 and thereafter inserting the end portion of the thin stainless steel pipe 1 to the inner portion of the pipe insertion hole 2d existing in both sides of the joint 2, as shown in a right half of FIG. 10. Further, the male thread portion 7 formed in the outer periphery of the end portion of the joint 2 is connected to the female thread portion 8 of the nut 4 outwardly fitted to the thin stainless steel pipe 1 by turning the nut sufficiently in advance until the joint contact surface 9 comes into contact with the opening end portion 2a of the joint 2 in a fastening manner. Accordingly, as shown in a left half of FIG. 10, the chevron type projection portion 5 of the thin stainless steel pipe 1 is pinched by the corner portion 2b of the joint 2, the inclined notch portion 10 of the nut 4 and the packing 3 so as to be fixed, and the packing 3 is closely attached to the inclined surface 5b of the chevron type projection portion 5, the packing pressing surface 6a and the packing outer peripheral contact surface 6b corresponding to the inner side surface of the packing fitting portion 6, and the joint contact surface 9, thereby preventing the leakage of water leaking out from the gap of the connection portion between the thin stainless steel pipe 1 and the joint 2.